The survey by eMarketer represents a setback for Yahoo's effort to return to its glory days as an Internet pioneer.

The report said Google will extend its domination of the global digital ad market this year, with a 31.45 percent market share, while Facebook will see its share grow to 7.79 percent.

Yahoo's ad revenues will increase by around 2.7 percent to 3.53 billion USD but its growth will be slower than the rest of the fast-growing sector, eMarketer said.

Microsoft meanwhile is expected to see 20 percent growth in ad revenues to 3.56 billion USD, for a 2.54 percent market share.

The total market for digital ads is expected to grow by 16.7 percent to 140 billion USD, the survey said. Facebook and Twitter are expected to see the fastest growth, eMarketer said, although Twitter's market share will remain below one percent.

The news comes with Yahoo set to report quarterly results, two years into the reorganization launched by chief executive Marissa Mayer.